Why Project Calendars Are Preferable to Global Calendars

One criteria on the scheduling review checklist used by a government naval command agency looks to confirm that calendars are defined at the project level. Why? Let’s explore this issue.

The Naval Facilities Engineering Command (NAVFAC) scheduling review checklist specifies that schedule calendars should be project-specific data and not global. Obviously, if you are submitting your schedule to NAVFAC then you have a compelling reason to use project calendars instead of global calendars. There are other sound reasons, however, that make project calendars preferable to global calendars. And these reasons may be the driving force behind the NAVFAC project level calendar criteria.

This article explores the reasons that Primavera P6 Professional project calendars are preferable to P6 global calendars.

The great thing about global calendars is that they are available to all users in the Primavera P6 Professional database, so all users have access to your defined global calendar. This is a double edged sword, however. Other users may not only use your global calendar; they may have the ability to actually change your global calendar. The implications are that their calendar changes are applied to any project schedule using that global calendar. Not good!

Another reason not to use global calendars is that exported global calendars clutter the recipient’s database. When you export a schedule assigned global calendars, those global calendars wind up in the global calendars list of the recipient importing your project. It’s amazing how quickly ones database becomes cluttered with rarely used global calendar definitions.

There is another reason not to export global calendars. Imported global calendars having the same name as global calendars already in the system are not renamed. They, however, inherit the properties of the global calendar currently in the system. So your global calendars of the same name, but in two different databases may not have the same global calendar definition.

Summary

Yes, it’s nice for your calendar to be available to all your projects and all your database users. Global calendars appear to be the way to go when creating a new calendar definition. But there are sound reasons for defining a calendar limited or restricted to a specific project.

Global calendars do not have the same security that project calendars have: other users can change your global calendar, and the respective schedules it’s assigned to. This alone compels schedulers to define project specific calendars. You may also clutter yours or your recipient’s global calendar list with rarely used calendars. There are also some export/import issues that may result in two global calendars of the same name, but with different date properties.

Primavera P6 Professional seems to favor global calendars as it makes it easy to convert project specific calendars into global calendars, but not vice versa. Despite this it is best practice to define calendars as project specific. 

reproduced from Tensix

S-Curves in Primavera P6 Professional

We’re frequently asked if Primavera P6 Professional is capable of displaying S-Curves. Sure, it can do that. You just have to know where to look.

This article is a ‘How To’ on S-Curves in Primavera P6 Professional, how to configure them and how to print them.

What is an S-Curve?

For those of you who are new to the topic, an S-Curve is a simple graph that plots costs, hours, units or other values (depending on the subject matter) over time. They are popular in Project Management because they give managers a quick and easy-to-understand view of cumulative budget, actual and remaining values over the project lifecycle. The term S-Curve denotes the tendency of the lines to form a shallow ‘S’ shape; flatter at the start, steeper in the middle and flattening off again towards the end. This shape is very typical of most projects as the effort ramps up in the beginning periods, stabilizes during the main execution phase and then starts to wind down again towards the Project’s completion.

Read the remainder of this post on  Ten Six

Conscientious use of constrains

Generally, constraints affect the dates, violates the network logic and one of the reasons for negative floats or irrationality on the schedule. But again this is based on your project requirements and these constraints could help you to provide a complete control of a project however no more than 10% of a project’s activity should be constrained. 

Constraints other than contractual ones are generally not used since they impose specific start and or finish dates and in some instances completely OVERRIDE the logic that is contained in the schedule. The idea is to let the logic determine the dates as opposed to using constraints to do this.

Early constraints (e.g. Must Start/Finish On or After) are a typically a shortcut to represent the outcome of related work that the scheduler is excluding from the schedule logic. This is justified only for interfacing work that - in total, including its initiation - is clearly outside the scope of the project scheduled (e.g. contractual access restrictions, customer-furnished info/eqpt/permits.) Using early constraints for in-scope work (or for external work that depends on in-scope work) removes that work from logical schedule analysis, overrides the logically-derived scheduled (early) dates of the constrained activities and their successors, and jeopardizes the validity of the entire logical model of the project including float calculations.

 Late constraints (e.g. Must Start/Finish On or Before) are typically imposed to represent external obligations or commitments – aka “deadlines.” Such commitments can be imposed by contract (e.g. completion milestones) or by some other governing document (e.g. Project Charter, Board Instruction, Executive Tantrum, etc.) Late constraints can override the logically-derived (late) dates for the constrained activities and their predecessors, thereby complicating the interpretation of Total Float and identification of the “Critical Path.” Where multiple late constraints are applied in a network of related activities, Total Float becomes unreliable as an indicator of driving logic; then other methods of logical analysis must be used.

Other constraint types (Start/Finish On, or Mandatory Start/Finish) are even more restrictive with respect to driving logic flow – they are rarely if ever justified.

It is true that ALL constraints affect total float computations but so do the calendars being used, the remaining durations, the logic, the lags, the TIMES etc. So I would re-iterate that this clause was included in the scheduling specifications because constraints impose specific start and or finish dates and in some instances completely OVERRIDE the logic that is contained in the schedule.

Tracking Labor Units on Multiple Resourced Activities In Primavera P6

If you have activities with multiple resource assignments in your schedule, it’s typical even with the best of schedules that your resources don’t always work the exact hours they were originally planned to. Do you know how to track labor units in Primavera P6 so that your progress updates on the multiple resourced activities accurately reflect the actual labor units expended?

It is important when tracking the labor units of activities, particularly, activities with multiple resource assignments, to follow the proper sequence for the procedures. If the procedures are not followed in the prescribed order, then Primavera P6 will compute erroneous labor units when recalculating the schedule.

Read the Post on TenSix

Why You Should Avoid Mandatory Activity Constraints

If you just cannot get your schedule to match an important finish milestone deadline you may be tempted to go “thermonuclear” by inserting a Mandatory Finish constraint on the milestone. You’ll definitely get your important finish date this way, but there will be collateral damage to your schedule. Let’s explore this.

If you want a child to stay away from a stove top burner you could simply tell the child ‘do not touch’. A more indirect approach is to tell them about the stove, and in doing so provide them knowledge that warns them to stay away. The later approach is our intent today in explaining mandatory constraints. We are telling you how mandatory constraints work not so you will haphazardly use them, but so that you will know enough to be cautious and even wary of their use.

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How to Show the Baseline Critical Path In P6

All project controls professionals know how critical is it to monitor our project’s critical path. And we all know that comparing our project performance to a baseline is also essential. Most of us are doing this critical path and baseline monitoring in Primavera P6 every day. But what about monitoring our project’s critical path vs our baseline critical path in P6?

Of course, as we execute a P6 schedule, over time, the schedule will diverge from it’s baseline. The myriad of changes, out-of-sequence fixes, late or early work will be inevitable. And it will happen that those changes will also affect our original critical path.

Are we able to check our path and compare it to the baseline critical path in P6?

From Plan Academy

Showing Relationship Arrows between Schedule Activity Bars and Not Baseline Bars

In a Primavera P6 training class last week, one attendee asked how to switch the relationship arrows from connecting the baseline bars to connecting the current progressing schedule activity bars. Once the project has been baselined and progress has been entered, you will notice that the relationship arrows are connecting your baseline bars and not the current schedule bars. How do you correct this so you can clearly see the relationships between tasks on your progressing schedule? Well, there is a simple way to make the relationship arrows connect the bars or tasks on your progressing schedule instead of the baseline bars.~

Read the article on Ten Six